Apple has released a new version of iTunes. Version 4.2 includes the ability to sign in and buy music from the iTunes Music Store using either an AOL or Apple Account, view the iTunes Music Store in a separate window, and offers a number of performance improvements.
A new tag was introduced with this update, called grouping. It is a user-defined tag which enables better categorization. Usage possibilities range from sub categories of genres to classical movements. This should make for more flexibility with both smart playlists and general sorting.